Tampa, Florida -- The city of Tampa is seeking answers from a contractor after one of its workers was caught on video dumping concrete into the Hillsborough River near MacDill Park. The worker was fired.

Matthew Von Dorhre was walking past the Riverwalk project Monday when he saw it happen. "I know it's not the legal, not the right thing to do, but I turned an eye to it," he said.

Then the next day, he saw the same thing. "I couldn't believe they were doing it again the second time," he said.

So he captured the dumping on video with his camera.

A contractor was caught dumping concrete in the Hillsborough River.

And the city wanted answers.

"We told them don't bring any more concrete on site. We need a formal written notice - why, how, how many times. Since then they've told us they'll do their washouts on site, not over the river at all," a city spokesperson said.

A crew from Johnson Bros. was back at the site Thursday and a worker said one person was fired and others have been reprimanded. The company failed to respond to several messages.

A concrete worker was fired and the company put on notice after concrete was dumped in the Hillsborough River.

The city hopes the company changes how it works and moves ahead with the $9 million contract.

"Right now we hope they remedy it. and move forward successfully," the spokesperson said.

Von Dorhre said it's good the city paid attention to the dumping, but the action needs to stop.

"A slap on the wrist may be OK - but if this is something done continuously then that's a problem," he said.

City officials don't expect this to slow the project down, which should be complete by the new year.

The spokesperson added that inspectors were at the site on Thursday and the crew was following proper procedures.

The Hillsborough County Environmental Protection Commission was also onsite to review the disposal area used Thursday, and found it to be acceptable.

"Please remember that the contractor notified us this morning that instead of continuing to dispose of washout on the barge over the River, it would be done on land, which is what these pictures show," the EPC said.

"Johnson Bros. did turbidity tests late Wednesday, which measure the amount of particulates in the water, and has shared the results with us per contract. The turbidity of the water is within normal range and way below any threshold, is great news. (The threshold is 29 Nephelometric Turbidity Units. The sample readings were 2.53 NTU & 3.62 NTU.) The results are consistent with other samples taken earlier in the project. A hard copy of that report is also available.